Sudden cardiac death is the leading cause of death in the United States, with one person dying every two minutes. Most sudden cardiac death is caused by ventricular fibrillation (“VF”), in which the heart's muscle fibers contract without coordination, thereby interrupting normal blood flow to the body. The only known effective treatment for VF is electrical defibrillation, in which an electrical pulse is applied to the patient's heart. The electrical pulse must be delivered within a short time after onset of VF in order for the patient to have any reasonable chance of survival. Electrical defibrillation may also be used to treat shockable ventricular tachycardia (“VT”). Accordingly, defibrillation is the appropriate therapy for any shockable rhythm, i.e., VF or shockable VT.
One way of providing electrical defibrillation uses an external defibrillator. External defibrillators send electrical pulses to the patient's heart through electrodes applied to the patient's torso. External defibrillators are typically located and used in hospital emergency rooms, operating rooms, and emergency medical vehicles. Of the wide variety of external defibrillators currently available, automatic and semi-automatic external defibrillators (referred to collectively as “AEDs”) are becoming increasingly popular because they can be used by relatively inexperienced personnel. Such AEDs are also especially lightweight, compact, and portable. AEDs are described in U.S. Pat. No. 5,607,454 to Cameron et al. entitled “Electrotherapy Method and Apparatus” and PCT Publication No. WO 94/27674 entitled “Defibrillator with Self-Test Features”, the specifications of which are incorporated herein.
AEDs provide a number of advantages, including the availability of external defibrillation at locations where external defibrillation is not regularly expected, and is likely to be performed quite infrequently, such as in residences, public buildings, businesses, personal vehicles, public transportation vehicles, etc. Because AEDs are designed to be small, lightweight and easy to maintain, AEDs generally do not feature a paper based ECG recorder.
One drawback to using an AED is that it typically does not provide a way to review the historical ECG data since AEDs display only the currently monitored information. ECG review is accomplished via a paper-based ECG print-out. Because of the added weight associated with an ECG printer this is a feature that is typically included in the larger multi-feature defibrillators (for example, the CodeMaster 100 by Hewlett-Packard). As AEDs have become more common (e.g. in airports, hotels, cruise ships, and airplanes), the number of times responsibility for the care of a victim is transferred increases. For example, instead of the traditional paramedic to emergency room transfer, the situation now exists where a first responder (such as a lay person, or airline attendant) may be superceded by a firefighter or police officer and then a paramedic prior to being taken to the emergency room at a hospital. Each time responsibility for a patient is handed off to a more advanced caregiver, it is important to be able to quickly transfer relevant historical treatment information. However, while professional caregivers are accustomed to providing a thumbnail summary of prior treatment to an advanced caregiver, such as an emergency room physician, the same is not true for a lay responder.
Thus, when emergency response personnel are called to the scene of a cardiac arrest or a patient is transferred to the emergency room, the ability to quickly review the incident (or ECG history) is desirable since the initial lay responder may not be in a position to accurately describe the early portions of the treatment. This is particularly important, because ECG history can impact subsequent treatment. Further, it is desirable to note the various treatments applied at the scene and record the patient's response. Such information might help trained cardiologists, reviewing the information, to rule out certain disease or defect conditions that potentially could afflict the patient prior to administering treatment.
U.S. Pat. No. 4,610,254 to Morgan et al. for “Interactive Portable Defibrillator,” discloses a portable interactive defibrillator that records patient status information such as ECG as well as user-supplied information that is input in the form of prompts from the defibrillator to the user. Morgan further discloses the use of a tape recorder medium to record relevant medical information during the use of device. The recorder is a two-track recorder—one track for ECG and other patient data and the second track for audio data to record the voice of the response personnel as well as sounds indicating that a shock has been delivered to the patient. The tape recorder allows the data to be removed from the device for subsequent review.
U.S. Pat. No. 4,945,477 to Edwards for “Medical Information System,” discloses a system for recording and presenting information pertaining to a medical event such a cardiac arrest. Edwards' system records events identified by the defibrillator and stores these events for human-readable replay. Defibrillator-identified events (termed “annotations”) can be effected by the pressing of a button on the defibrillator by the user or by the recognition that a medical event (e.g. arrhythmia) has occurred. As a memory space saving technique, Edwards describes a means in which his system stores three second intervals according to priority of events. Events having higher priority may well overwrite events of lower priority.
U.S. Pat. No. 5,785,043 to Cyrus et al. for “Method of Creating A Report Showing a Time Correlation Between Recorded Medical Events,” describes a system for retrieving and presenting information recorded by an AED on a personal computer.
While these systems do provide some level of data recording and subsequent play-back, they do not provide a mechanism to play back information recorded during treatment of a patient on the device screen. Further, there is no provision for review of the data while the device is still connected to a patient.
Thus, it is an object of the present invention to provide medical personnel with an AED that allows the user to review the recorded data on the device. Ideally, this information can be reviewed both on-line (i.e., when the device is attached to the patient) or off-line (after the device has been used to treat the patient).